Low-density web-like cushioning structure of cellular filamentary material



Dec- 23, 1969 F. H. FISH. JR.. ETAL 3,485,711

LOWDENSITY WEB-LIKE CUSHIONING STRUCTURE OF CELLULAR FILAMENTARYMATERIAL 2 Sheets-Sheet l Filed June 23, 1965 IGZ M O nn. 1 JE D C...nn. N rr .l H U A V| N m E R D R C nn un A 0 A .l..| EL s.. TL .Inn UAUs EEE ER LC JH RM L G RCL ml Eon rr. n N U D A Dn /o o B0 ...l P 0 u Nun vl o o/ BCI A l. D| 0 .IJ D E 0 0 U w N S P vl l. 00 R ww l. l \\JLIC \.l.\l`/ Q C la 5 2 0 2 l N 0u. 5 5/ nl L f\ D A 0 .L m E v s s E RDI um 0 5 C 0 ATTORNEY F. H. FISH, JR, ETAL Low-DENSITY WEB-LIKECUSHIONING STRUCTURE oF CELLULAR FILAMENTARY MATEMAL 2 Sheets-Sheet 2Filed June 23, 1965 o O4 o /D a Xo O o G o//lp G N N R11 o Dn| Ml! EN noR0 f .|11 0l 0H Ewuv DTS BU U Pv x C n v nU O 0 0 O O 0 0 0 0 o 0 0 o 00 0 O O o nu .Iv .4. 11.... nsf'. Il. m 9 ou 7. 6 5 d.

% COMPRESSION AT 25 PSI (|16 HGJCHZ) INVENTORS FLOYD HAMILTON FISH, JR,CAWLEY RICHARD STINE ATTORNEY nited States Patent O US. Cl. 161-150 9Claims ABSTRACT OF THE DISCLOSURE A resilient, low-density cushioningstructure, suitable as a carpet underlay, comprising randomly arranged,closed-cell, pneumatic, polymeric, cellular filamentary material, isdisclosed. The material has superior cushioning properties atexceptionlly low area-Weight.

For many flooring applications it is desirable that the flooring surfacehave resilient, luxuriant underfoot aesthetics. Usually it is alsodesirable that the surface feel warm as a result of thermal insulationprovided by the surfacing material. Carpets and rugs of 'numerousconstructions have been used to provide these functions for ages. Ingeneral, carpets are comprised of some dimensionally stable base layerto which textile yarns are attached in such a fashion as to create awear-resistant decorative surface. These textile yarns provide levels ofunderfoot aesthetics and insulation approximately in proportion to thequantity of yarn employed per unit of carpet-area, at least for similarcarpet-constructions. Ex-

erience has shown that the quantities of yarn required for the desiredproperty levels are so great as to render carpets, as a sole coveringover rigid floors, prohibitively expensive for many potentialinstallations.

Carpet-underlays were developed for use between the carpet and the rigidfloor, these underlays also providing resiliency and heatandsound-insulation properties. ln general these underlays are much lessexpensive, less physically strong, and less Visually attractive than theoverlying carpets, but their use beneath carpets imparts the desiredunderfoot aesthetics and insulation to the combined floor-covering witha great reduction in the quantity of expensive textile yarn employed. Itis known, moreover, that the use of certain kinds of underlay beneathcommercially available carpets can increase the useful carpet life-spanby a factor of two, or more.

The specification of required properties for carpetunderlays isparticularly diflcult because of the wide variety of conditions to whichthey are subjected. These include sustained compression under medium tolarge loads exerted, for example, by furniture legs. Simultaneously,they include transient walking loads ranging from the modest ones ofmens feet and shoes to the very concentrated loads applied by ladiesnarrow spiked heels. After removal of sustained loads, the underlayshould regain substantially its original thickness within a reasonableperiod of time so as not to leave a permanent indentation. Undertransient loads, however, the underlay should softly cushion by rathergreat transient thickness reduction, again with regain of substantiallyits original thickness. These load-support, cushioning, and recoveryproperties should also be retained during years of use. In many respectsthese requirements lead to opposed property specifications, and allknown carpet-underlays embody some degree of compromise.

One well-known type of underlay is comprised of animal and/or vegetablefibers in a felt, with or without impregnation by rubber latexes. Theseare hereinafter ice collectively referred to as hair/ jute underlays,for brevity. Hair/ jute underlays are dense and heavy, have lowresilience, decrease usually no more than 50% in thickness under anyload characteristic of the end-use, become more permanently compactedand even less resilient with use, and exhibit severe permanentdepressions after removal of sustained loads. They moreover can causeextreme dusting, repugnant odors from mildew and degradation, andallergy problems.

Certain sponge-rubber underlays, with either plain or deeply patternedsurfaces, constitute the currently most popular products against whichother carpet-underlays are compared. In order to provide the desiredproperties, they must be relatively dense and are7 consequently,expensive. When new, they are very luxurious under foot, but many bottomout rather easily under loads greater than charactersitic of walkingloads. Regain of original thickness upon removal of either transient orsustained loads is rapid and substantially complete. After only two tothree years of use, however, many sponge-rubber underlays became sodegraded from exposure to the atmosphere that they lose much of theirresilience, become physically weak, easily crumble, and frequently stickto adjacent floor and carpet surfaces.

More recently, resilient foamed polyurethanes have been introduced forcarpet-underlay use but, at economically competitive densities andarea-weights, bottom out even more readily than sponge-rubber. Inaddition, they are physically weak and easily torn even when new. Apeculiarity of resilient polyurethane foam is a compression behavoircharacterized by initial stiffness, followed by extensive collapse withessentially no increase in load, and suddently terminating in asubstantially incompressible state. This intermediate unsupportedcollapse can give a walking preson a sensation of falling with abrupttermination of the fall, and it is undesirable both because it upsetsthe walkers sense of balance and because it does not properly supportcarpets to increase their useful life-span.

Various forms and combinations of the above three types of materialsconstitute substantially all the commercial Carpet-underlays currentlyavailable.

This invention provides a novel carpet-underlay at areaweights greatlyless than for any materials heretofore available. Another provision is acarpet-underlay for which the resistance to compression increasescontinuously with increasing compressive load; i.e., there is nounsupported collapse, and there are no points of inflection in theloadcompression curve. A further provision is an underlay whichcompresses only 45 to 70% in thickness under a 25 p.s.i'. (1.76kg./cm.2) load uniformly distributed over a flat indentor at least about4 in.2 (about 26 cm?) in area. Still another provision is acarpet-underlay which is substantially unchanged in chemical andphysical properties during normal life-times in use. A still furtherprovision is an underlay which, used between a carpet and rigid floor,imparts luxuriant underfoot aesthetics. Yet another provision is acarpet underlay which recovers substantially all of its initialthickness after transient or sustained compressive loadingcharacteristic of the enduse.

These and other provisions result from the following invention which isa resilient, low-density, web-like cushioning structure, suitable ascarpet-underlay, comprised of closed-cell, pneumatic, polymeric,cellular material in lamentary form, said filamentary material beingrandomly disposed within said structure to provide numerous crossings offilament-portions, being consolidated so as to distort iilament-portionsaround one another and provide substantial areas of iilament-to-lamentengagement such that the average ratio of volume of said lamentarymaterial to total volume of said structure is at least 0.4, and beingbonded at least Within portions of said structure to permanently retainsaid consolidated volume, major portions of said filamentary materialhaving a density of from about 0.008 to 0.06` gm./cc. and containingwithin the cells thereof about 6y to 40 gm. of an impermeant inflatantper 100 gm. of polymer.

The above-described cushioning structure possesses a combination offeatures which makes it outstandingly superior to previously known typesof carpet-underlay, It has the coherency and strength of a molded sheetand yet, being based upon a lamentary material, comprises a porous,breathable open network. The pneumatic character of the filamentsinsures that there will be no unsupported collapse as a compressive loadis increased. Moreover, the fact that the pneumaticity is derived from amyriad of small, closed, gas-containing cells in the laments, and notmerely from an impervious casing about porous filaments, means that theload will be more evenly distributed within and across the structure.Still another feature of considerable importance is the fact that thefilaments are in a particula-rly distorted, e.g. stressed, conditionowing to the consolidation-hence increasing the load-support property.

The invention Will be further described with reference to the drawingswherein:

FIGURE 1 represents an unconsolidated filament-batt from which theproducts of this invention can be prepared.

FIGURE 2 is the batt of FIGURE 1 consolidated to a cushioning structureof this invention.

FIGURE 3 is a preferred, one-side-embossed cushioning structure of thisinvention.

FIGURE 4 is the cross-section yL10-40 of the underlay 'of FIGURE 3showing it installed on a floor beneath a carpet.

FIGURE 5 is a load/compression diagram comparing certain products ofthis invention with conventional underlays.

FIGURE 6 is a comfort map for various underlay products.

`Cushioning structures according to this invention can be regarded asbeing in sheet form; i.e., their parallel broad faces are very extensivecompared to the thickness, which is about 0.1 to 1.0 inch (0.25 to 2.5cm.) and preferably from 0.2 to about `0.45 inch (0.50 to about 1.15cm.). The preferred thicknesses correspond to those of commerciallyavailable carpet-underlays. These cushioning structures are comprised ofone or more closed-cell foam-filaments, the cells of which containimpermeant inflatant gas (as more fully described hereinafter). Becauseof the presence of impermeant inflatant gas, an osmotic gradient for theinward permeation of air exists, and the gas pressure within the closedcells exceeds atmospheric. Consequently, the foam-filaments areinflated, resilient, and pneumatic so as to be relatively resistant tobending. Either continuous or staple filaments can be used.Length-to-diameter ratio for staple filaments is preferably at least inorder to insure adequate strength and stability for the ultimatecushioning structure.

In forming these cushioning structures, foam-filament are laid down insuch a fashion as to build up the thickness while creating a randomdistribution of filament directions in the plane of the structure.'Thus, there are numerous crossings of filament-portions and considerablepenetration of portions of filaments generally positioned at onethickness level into adjacent thickness levels. Area-weight offoam-filaments in a cushioning structure should be substantiallyconstant when measured on areas with linear dimensions very much largerthan the filament-diameter. In order to achieve satisfactory uniformityof filament-Weight distribution, it has been found that the thickness ofthe structure at any point should be equivalent to at least 3 times theaverage contribution of a single filament to the thickness in theimmediate area.

Stated differently, the thickness of the structure is equivalent to atleast 3 filament-thicknesses regardless of the state of filamentdistortion in that area. Area-weights ot' the structures of thisinvention, based only on the weight of filaments, are broadly from about1.0 to 10 oz./yd.2 (34 to 340 gm./m.2) and preferably from about 1.5 toabout 5.0 oz./yd.2 (50 to 1720 gm./m.2); but structures of higherarea-weight can also be provided, if desired.

As initially deposited in a filament-batt, the pneumatic filaments aremuch too stiff and too light to drape or bend around one another attheir crossings. Only point-contacts between crossing filament-portionsare made, and these are rather widely spaced. Unless forced into aconsolidated state, the filaments occupy only a small fraction of theeffective volume of the batt, this volume fraction usually being lessthan about 0.25. When such non-consolidated structures are compressed,thickness reductions of from 25 to 50% can result from loads of onlyabout l p.s.i. (70 gm./m.2). Such soft cushioning results, primarily,because initial thickness distortion is a combination offilament-bending and filament-compression at the point-contactfilament-crossings Where the volume of gas being compressed is extremelysmall compared to the total volume of the batt.

Compressive loads to be resiliently supported by carpetunderlay arecharacteristically of the order of 25 p.s.i. (1760 gm./crn.2), orgreater. In order that the filamentbatts can support these loads withoutbeing excessively thick or initially too soft, it is necessary that thebatts be consolidated, that is, reduced in thickness until the filamentsare forced to bend around one another, thus forming more numerous andextensive interfilament contacts. In effect, the pneumatic filaments inthe products of this invention are pre-loaded. Volume fraction offoam-filaments exceeds 0.4 but is less than 1.0; i.e., filament identityis retained and numerous interlament passageways remain to provide abreathable, open, filamentnetwork.

Interfilament bonding must be provided to prevent spontaneousre-expansion of the consolidated batt to its unconsolidated state.Consolidation does not decrease the super-atmospheric pressure withinthe closed cells of the filaments, except in minor areas where the foamis either completely collapsed or melted to effect bonding.Consequently, the filaments remain pneumatic and Will regain theirunconsolidated orientation unless constrained.

Referring now to the figures, FIGURE l represents an unconsolidatedfilament-batt generally indicated by the numeral 10 and comprised ofinflated filaments 11 which are undistorted except for perhaps minorfolds along some filament-lengths where curvature is excessive. FIGUR-E2 represents one cushioning product 20 according to this invention andis the batt 10 of FIGURE 1 consolidated normal to its faces 13 toprovide a carpet underlay, or similar cushioning batt, with aspace-filling density based on filament-weight of from about 0.7 to 1.16lb./ft.3 (0.011 to 0.026 gm./cc.). Such plane-surfaced carpetunderlaysare kept consolidated by adhesives introduced to the batts in such a wayas to form bonded interfilament crossings while the filament-batt isconsolidated.

While plane-surfaced structures 20 as shown in FIG- URE 2 are effectiveforms of this invention, other preferred forms are consolidated lbyembossing. By embossing is meant herein applying to the surface of acushioning structure a repeated and nested set of geometric shapesformed from simple line elements, straight or curved, such that eachline element is the common boundary of two geometric shapes (exceptingthose at the edges of, for example, the embossing roll). Examples ofsuch suitable geometric shapes are triangles, diamonds, rectangles,hexagons, and the like. Along each line element the cushioning structureis thinnest and densest, while at the center of each shape thecushioning structure is thickest and least dense. The width of each lineelement can vary from that of a knife-edge to about 0.25 inch (0.635cm.). `It should be at least as long as times the maximum transversecross-sectional dimension of the fully inflated filament employed but nogreater than about 30 times that dimension. Larger patterns may fail toproduce sufficient consolidation in the thicker areas. Less than 50%,and preferably less than 25%, of the surface area of the cushioningstructure should be reduced to the minimum thickness. The filamentsalong the line elements are stabilized in this reduced thicknessconfiguration thereby rendering the cushioning structure strong andtear-resistant while simultaneously providing the con- `straint whichkeeps the whole structure consolidated. Thickness stabilization alongthese embossed lines can result either from applied adhesive or bythermal fusion of the polymeric foam.

FIGURE 3 is a perspective view of a carpet-underlay 30 of the preferredone-side embossed construction. FIG- URE 4 is a cross-sectionalrepresentation of the underlay 30 of FIGURE 3 as shown at l0- 40, FIGURE4 including in addition an overlyingI carpet 41 and supporting rigidfloor 43. With the rounded protuberances 4S, formed by embossing,against rigid floor 43 this form of the invention has particularadvantages. Since only a small area of each protuberance 45 contacts thefioor, and since this is its lowest density, softest portion, theunderlay is more readily compressed by light loads on overlying carpet41. As the compressive load increases, more area of each protruberance45 comes into contact with rigid fioor 43, and the density of compressedcushioning structure 30 in that area increases. The resistance tocompression thereby increases with increasing compression, as is mostdesirable, and the underlay is most luxurious underfoot for the lightertransient loads. Under heavy loads, however, the underlay remainsresiliently compressible because, in the limit, it becomes substantiallya uniform layer of compressed gas. Moreover, since the gas is enclosedin closed foam cells, it quickly returns the underlay to its originalthickness by its expansion.

A further advantage of the preferred structure 30 of FIGURES 3 and 4 isthat, even if some air ultimately escapes from the cells under sustainedloads, the underlay immediately regains essential fiatness of its planesurface 47 to support the overlying carpet 41 without temporary apparentindentation. The collapsed protuberance(s) 45 may pull away from thefioOr 43 for a short time, but impermeant infiatant within thefoam-cells provides an osmotic gradient for re-entry of displaced airand eventual recovery of the protuberance(s) 45 to substantially theoriginal size and shape.

Maximum thickness of embossed underlay 30 is also the effectiveunderlay-thickness between carpet and floor. Underlay-density computedfrom this maximum thickness and from the constant area-weight offoam-filaments should be in the range from about 0.3 to about 1.6lb./ft.3 (0.005 to 0.026 gm./cc.). This minimum density usually occursonly near the center of each geometric shape, the density increasingalong the line elements 31 to a maximum of from about 8 to 100% of thedensity of the unfoamed, solid polymer.

Cellular filaments for use in the products of this invention requirecertain characteristics and properties. A particularly essentialcharacteristic is that they have a major proportion of closed cellssince open cells cannot confine the required impermeant inliatant andcannot provide the pneumaticity from which the cushioning propertiesderive. Visual or microscopic examination is usually sufficient todetect whether closed cells predominate; but, otherwise, the closed cellcontent can be determined by the gas displacement method of Remingtonand Pariser, Rubber World, May 1958, p. 261, modified by operating at aslow a pressure differential as possible to minimize volume changes.

The cell-walls of suitable cellular filaments are composed of highmolecular weight polymers-usually synthetic organic thermoplasticpolymers. A `wide variety of both addition and condensation polymers canform cellular structures with the essential characteristics. Typical ofsuch polymers are polyolefins, polyamides, polyesters, andhalohydrocarbon polymers such as polyvinyl chloride and the like. Thefilaments are homogeneously foamed throughout; i.e., the outer surfacesare comprised of numerous cell-walls rather than being separatelyidentifiable casings or coverings. The pneumaticity and resilience ofthe products of this invention derive from gas confined within thefoam-cells, and these properties are provided at underlay area-weightsvery much less than can be obtained from filaments with dense casings.

Fully intiated filaments useful in constructing the products of thisinvention are recoverably yieldable with densities in the range fromabout 0.008 to about 0.06 gm./cc. A highly suitable class of cellularstructures has polyhedral-shaped cells defined by thin, film-likecell-walls. Such thin cell-walls are very fiexible, contributing greatlyto the yieldable nature of the filaments; and, as described hereinafter,are readily plasticized for `the inward permeation of impermeantinfiatant.

A particularly desirable type of cellular material is ultramicrocellularas described in U.S. Patent No. 3,227,664 to Blades et al., thedisclosure of which is incorporated herein by reference. These preferredstructures contain at least 1,000 cells per cc., the average transversedimension of which cells is less than 1,000 microns. Substantially allof the polymer is present in the cell-walls which are film-like elementsless than 2 microns, and preferaby less than 0.5 micron, thick. Thethickness of a cell-wall, bounded by intersections with other walls,does not ordinarily vary by more than i30%; and adjacent walls arecommonly of substantially the same thickness, i.e. within a factor of 3.Moreover, the polymer in the cell-walls exhibits uniplanar orientationand a uniform texture, as fully described in the aforementioned patent.

One of the features `of ultramicrocellular structures is the high degreeof orientation of the polymer in the cell walls, `which contributes tothe unique strength of these structures. A preferred class of polymersfrom which to make cellular filaments for use in the products of thisinvention is that class which responds to an orienting operation (eg,drawing of bers or films) by becoming substantially tougher andstronger. This class is wellknown in the art and includes, for example,linear polyethylene, stereo-regular polypropylene, 6-nylon, andpolyethylene terephthalate. Because most gases permeate throughpolyethylene terephthalate very slowly, it is particularly preferred.

An impermeant infiatant gas is one that permeates the cell-walls soslowly, as compared to air, that it is substantially permanentlyretained within closed cells, even under compression. The rate ofpermeation for any gas through a given polymer increases as itsdiffusivity and solubility increase. Accordingly, candidates forimpermeant inflatants should have as large a molecular size as isconsistent with a high vapor pressure, that is, a vapor pressure of atleast 50 mm. of mercury at normal room temperatures. Atmospheric boilingpoints for preferred impermeant infiatants are less than 25 C., andpreferably less than 15 C. Preferred impermeant infiatants are also fromthat class of compounds whose molecules have chemical bonds differentfrom those in the confining polymer, a low dipole moment, and a verysmall atomic polarizability, thus assuring insolubility in the polymer.

Suitable impermeant infiatants are inert materials selected from thegroup consisting of sulfur hexafluoride and saturated aliphatic orcycloaliphatic compounds having at least one fluorine-to-carbon covalentbond and wherein the number of fluorine atoms preferably exceeds thenumber of fluorine atoms preferably exceeds the number Of carbon atoms.Preferably these inliatants are perhaloalkanes or perhalocycloalkanes inwhich at least 50% of the halogen atoms are fluorine. Although theseinflatants may contain ether-oxygen linkages, they are preferably freefrom nitrogen atoms, carbon-to-carbon double bonds, and

reactive functional groups. Specific examples of useful impermeantinflatants include sulfur hexafluoride, perfluorocyclobutane,sym-dichlorotetraiiuoroethane, chlorotrifluoromethane,dichloroditiuoromethane, and chloropentaliuoroethane. Particularlypreferred because of its inertness, very low permeability rate, largemolecular size, and lack of toxicity is peruorocyclobutane with anatmospheric boiling point of about 6 C.

The presence of impermeant iniiatant gas within the foam-cellsguarantees full inflation of the filaments by providing an osmoticgradient for the inward permeation of air until internal pressures aresuper-atmospheric. If some air is lost during compression, the filamentsthereby spontaneously re-inate after removal of the load. Foam-filamentscontaining impermea-nt inliatant are seen to be durably pneumatic, asopposed to those inated only with air or with rapidly permeatingfo-aming agents. In practice, a certain minimum concentration ofimpermeant inflatant is required to provide these advantages. From aboutto about 40 grams of impermeant infiatant per 100 grams of polymer hasproved effective for use in carpetunderlay.

Fully inflated foam-filaments useful in the construction of the productsof this invention have major cross-sectional dimensions the range of0.025 to 0.25 inch (0.635 to 6.35 mm.) but are preferably in the rangefrom 0.050 to 0.100 inch (1.27 to 2.54' mm.). Although variouscross-sectional shapes can be formed, circular ones are usuallypreferred for which the circular extrusion orifices are easily made. Indeeply embossed carpet-underlay it is possible to reduce filaments alongthe line elements to solid polymer containing essentially no impermeantinfiatant. At other points, the necessary consolidation may severelyalter cross-sectional shape of the filaments. The specification oflevels of retained impermeant infiatant refers only to the major portionof the underlay in which the filaments remain inflated, howeverdistorted they may be in cross-section.

The determination of quantity of confined impermeant inatant is readilycarried out. A foam-filament with impermeant inflata-nt in its lcellsand at osmotic equilibrium with air has an internal partial pressure forair of about one atmosphere. Total internal cell pressure exceedsatmospheric by about the partial pressure of the impermeant intiatant.With these conditions, air buoyancy corrections to weights in air are,at best, only second order. Weight in air W1, of an inflated sample ismeasured. The sample is then reduced between heated platens to a solid,non-foamed film, after which its weight in air W2, is measured. Platentemperatures must, of course, be low enough that no weight changeattributable to polymer degradation can occur. Impermeant infiatantcontent I, in grams per 100 grams of polymer is then readily computedusing Equation 1.

100ml-W2) W2 (l) Other physical methods, such as gas chromatography orspectrophotometry, can also be used to determine concentration ofimpermeant inflatant.

When adhesives are employed in constructing underlay, they must adherewell to the filaments and be durably flexible so as not t0 fail duringcompressive exercising. A great variety of commercial latexes, bothnatural and synthetic, are suitable. Adhesive bonds must be elastic, butnot necessarily elastomeric. Elastomeric adhesives are, however,frequently employed. Types of adhesives found satisfactory includethermoplastic, thermosetting, heatcurable, melt, and the like. Sinceadhesives are normally applied in the form of dilute solutions ordispersions, those adhesives either soluble or dispersible in volatileliquids which are non-solvents for the polymer are preferred.

The amount of adhesive required for internal constraint against loss ofconsolidation depends on the type of adhesive and in what form it isapplied. Normally this amount is less than of the weight offoam-filament, and preferably less than about 25%.

Certain adhesives may have a tendency to yield a iinished product whichis somewhat noisy; i.e., the filamentsurfaces slip against one anotherduring compression to cause squeaky or scratchy sounds. This noise maybe largely overcome by applying a lubricant to the filament batt, suchas various silicone oils or detergents. In a preferred method oftreatment for silencing, which also provides decorative coloredsurfaces, the underlay-surface is first sprayed with a solution of theabove adhesives and a desirable dye and then dipped in a solution ofsilencer. Up to 100% or more, by weight of filaments may be added to thearea-weight of underlay in this manner. In typical underlayconstructions the weight percent of foam-filament varies between 20 and80. Although the proportional quantities of adhesive involved may seemvery large, it must be remembered that any addition of dense adhesive tothe ultra-low-density filaments in the products of this invention mustof necessity be a sizeable fraction by weight. Within the specifiedlimits, the quantity of adhesive employed leaves essentially unchangedthe openness and breathability of the consolidated filament batt.

In alternative forms of this invention, either or both surfaces can becovered with a variety of surfacing materials. Adhesively bondedsurfacing materials include various net-like fabrics, many nonwovenfabrics, foils of open-cell foams, and many commercial plastic filmssuch as those of polyethylene, polypropylene, polyvinyl chloride, andpolyethylene terephthalate. It is also advantageous in some instances tocoat or extrude onto the surfaces foamable compositions of, forinstance, rubber, polyurethane, or neoprene, which become self-bondedwhile at the same time expanding into an open-celled foam layer. Also,carpet pile yarns may be attached. Other variations will be immediatelyapparent to one skilled in the art.

For purposes of testing and comparing the products of this inventionwith previously available materials, a load of 25 p.s.i. (1.76 lig/cm2)was selected as characteristic of both transient and sustainedcompressive loading. Load vs. compression curves were obtained on ll by16 inch (27.9 by 40.6 cm.) underlay specimens using a 4 in 2 (25.8 cm?)round indentor with a fiat bearing face. Indentor speed of entry wasnominally 0.5 in./rnin. (1.27 cm./min.), and it was maintained up to aload of at least 25 p.s.i. (1.76 kg./cm.2). FIGURE 5 presents suchload-compression curves for four products of this invention and comparesthem with commercially available underlays. The upper heavy curve withinits shaded area is for a typical hair/jute underlay, the shaded areashowing the range covered by the general class of such hair/juteconstructions. The intermediate heavy curve and its shaded area likewiserepresent available, new, patterned` sponge-rubber underlays. The lowestcurve and shaded area are for various new polyurethane underlays.Overlaid in dashed lines are load-compression curves for 4 selectedunderlays of this invention.

Important advantages of the products of this invention are evident frominspection of FIGURE 5. First, they may be constructed with 25 p.s.i.(1.76 kg./cm.2) compression properties extending continuously from thoseof firm hair/ jute to those softer than sponge-rubber. Consumerpreference tests in which housewives walked on identical carpet samplesbeneath which were concealed several currently popular underlays and avariety of the products of this invention revealed a distinct preferencefor those underlays which, tested at a load of 25 p.s.i. (1.76kg./cm.2), compressed about 45 to 70% of their initial thicknesses. Thisproperty level, supplied only by the more expensive commercialunderlays, is Well within the range most characteristic of thosestructures of this invention. Finally, the shape of the load-compressioncurve for the underlays of this invention is different from and improvedover those for known underlays. Products of this invention decrease inrate of compression continuously with increasing load. Bothsponge-rubber and polyurethane foam compress rapidly at low loads,decrease this response precipitously at or below p.s.i. (0.35 kg./cm.2),and compress quite slowly thereafter.

In addition to satisfactory load/ compression behavior in one cycle ofcompression, it is also necessary that carpet underlays remainresiliently compressible under cyclic loading at the end-use load. Thisis indicated by dynamic modulus for which low values characterizesuperior performance. Dynamic modulus, Z, is best defined by its methodof determination. Sample size, indentor, and apparatus are the same asfor load/compression determination. The sample is cycled between and 25p.s.i. (1.41 and 1.76 lig/cm?) loads 10 times with about 0.5 inch/ min.(1.27 cm./min.) indentor rates for both compression and recovery andwith no time-delay *between cycles. A secant modulus to the tenthcompression cycle is dynamic modulus in p.s.i. (kg/cm?) Computation isaccording to Equation 2.

(J2-C1 (2) wherein AL is 5 p.s.i. (0.35 14g/cm2), C2 is percentcompression at p.s.i. (1.76 kg./cm.2), C1 is percent compression at 20p.s.i. (1.41 kg./cm.2), and C is computed from ho-h ho (3) wherein h issample thickness at a given load and 1z0 is uncompressed original samplethickness. Table I lists pertinent dynamic modulus results for 31commercially available carpet-underlays and 22 different experimentalsamples according to this invention.

fragile items such as easily bruised fruit. They are also useful forthermal insulation in walls of buildings, in refrigerated containers,and the like.

The following examples are illustrative of the present invention but arenot intended as a limitation thereof except as provided in the appendedclaims. Where tensile strength is specified it is the force per unit ofwidth at tensile failure for a 3 inch (7.6 cm.) wide and 7 inch (17.8cm.) long sample clamped in jaws separated by 5 inches (12.7 cm.) andmoved apart at 5 in./min. (12.7 cm./min.). All parts and percentages areby weight unless otherwise specified.

EXAMPLE I Ultramicrocellular filaments were prepared by extrusion of afoamable composition from a l-liter cylindrical pressure vessel througha 5-hole die into the ambient atmosphere. Charged to the vessel underanhydrous conditions were the following:

Polyethylene terephthalate gm 400 Methylene chloride (at -25 C.) ml--350 1,1,2-trichloro-l,2,2-tri1iuoroethane (at -25 C.)

ml Peruorocyclobutane gm 52 The polyethylene terephthalate was ahomopolymer with relative viscosity (RV) of about 41. Relative viscosityas used herein is the ratio of absolute viscosities at 25 C. of polymersolution and solvent, with the solvent being itself a solution of partsof 2,4,6-trichloropheno1 in parts of phenol and with the polymersolution containing 8.7% polyethylene terephthalate. Before use, thegranular polymer was dried at 220 C. for 16 hours under vacuum with asmall nitrogen bleed. Liquid foaming agents which may replace methylenechloride in the extrusion of ultramicrocellular polyethyleneterephthalate TABLE I.DYNAMIC MODULUS COMPARISONS Average MinimumMaximum No. of Class Types p.s.i. (kg/cm?) p.s.i. (kg/cm2) p.s.i.(kg./em.2)

Hair/Jute 1 11 631 (44. 4) 539 (37. 9) 759 (53. 4) Sponge-Rubber(patterned) 6 583 (41.0) 526 (37. 0) 42 (45. 2) Sponge-Rubber(premium-fla 6 420 (29. 6) 333 (23. 4) 184 (a5. 2) Polyurethane 8 1, 288(90. 6) 820 (a8. 3) 1, 60o (113. 0) This Invention 22 390 (27. 4) 240(16. 9) 547 (28. 5)

From Table I it is quite apparent that the underlays of this inventionhave the lowest dynamic moduli and are, therefore, more resilientlycompressihle under enduse loads. These results are shown graphically inFIG- URE 6 which is a comfort map for carpet-underlays. Area I enclosespresently available hair/jute candidates. Area II (and its one widelydifferent point) the premium fiat sponge-rubber candidates, Area III theWeihe, nipple, etc. patterned sponge-rubber candidates, and Area IV thecandidates based on polyurethane foams. Variously shaped points indicateunderlay according to this invention, as completely described `inappended examples. It will be seen from FIGURE 6 that thecarpet-underlay of this invention has superior dynamic modulus over abroad range of percent c-ompression values, including the most preferredrange.

As is shown in the examples, these products have excellent recovery fromboth transient and sustained loads, and they have high tensilestrengths. They also maintain their integrity and cushioning over a longlife-time, do not dust, are non-allergenic, and do not decompose tocreate foul odors. Not only do they provide carpetuuderlay ofunprecedentedly low area-weight, but their load-compression propertiesare superior to any heretofore known carpet-underlays.

Being particularly useful as carpet-underlay, the products of thisinvention are not so limited. Thus they serve in numerous cushioningapplications such as in the walls of cushioning cartons or as separatorsheets between foams include ethylene chloride, chloroform, and carbontetrachloride.

Each hole of the extrusion die was 0.003 in. diameter by 0.006 in. long(0.0762 rnrn. x 0.1524 mm.), and the die was attached to one end of thecylindrical pressure vessel. A sandwich of screens was affixed upstreamfrom the extrusion holes being 50, 325, 325 and 50 mesh screensrespectively (U.S. Sieve Series). The sealed pressure vessel was rotatedend-over-end while being heated. With the temperature of the contents at213 C., rotation was stopped with the die facing downward and held thatway for 2 minutes to allow drainage of the solution before opening thedie holes. In this period, connection to a 1200 p.s.i.g. (84.4 kg./cm.2gage) nitrogen ballast tank was made through a valve in the top of thevessel. About 40 minutes were required to extrude all of the foamablecomposition.

The extruded filaments expanded to their maximum diameter near the faceof the extrusion die, but thereafter rapidly collapsed due tovaporization and loss of methylene chloride, to a density of about 0.065gru/cc. By subsequent heating for a few minutes at about C., air coulddiffuse into the closed cells to re-expand the filaments to theirmaximum diameter of about 0.010 inch (0.25 mm.). Filaments produced insuch a way will generally have a density of from 0.025 to 0.03 gm./cc.in the fully inflated state and will retain within their closed cellsfrom 1.0-1.5% of perfluorocyclobutane and about 5% of thetrichlorotritiuoroethane impermeant 11 natants (percentages by weight ofthe expanded filaments).

These filaments were to be used in the construction of a carpet-underlayspecimen. Accordingly, the iilaments were collected by and passedthrough a 0.25 inch (0.635 cm.) diameter pipe located several feet belowthe extrusion die and fed with a downward-directed air stream from asupply at 20-25 p.s.i.g. (1.4 to 1.8 kg./cm.2 gage). Between the die andthe pipe was placed a magnesium bar over which each iilament was passed.About 4 feet (1.22 m.) below the exit end of the pipe, a large aluminumplate was held for randomly collecting the filaments. Water was iinelysprayed onto the filaments from a paint spray-gun (Binks Mfg. Co. TypeNo. D5661) located at the level of the air-pipe. It was known that,without the added weight of water, the extruded iilaments would be blownoff the aluminum collection plate by the air jet. The aluminum plate washeld by hand and moved in such a way as to build up a uniformly thickbatt about 3.5 inches (8.9 cm.) thick. An 8 X 8 inch (about 20 x 20 cm.)square cut from this batt was sliced to provide two squares, each ofabout one-half the original thickness. These were designated A and B, Bbeing slightly thinner than A.

Batts A and B were converted to carpet-underlay specimens by the samegeneral procedure. Expanded-metal sheets were placed on one face of eachsample, each metal sheet being about 0.040 inch (1.02 mm.) thick andhaving diamond-shaped openings with approximately 1.5 X 0.5 inch (3.8 x1.26 cm.) diagonals. Each opening was separated from the next by a stripof metal approximately 0.2 inch (5.5 mm.) wide. Each sample with itsaligned expanded metal plates in place was put on one platen of ahydraulic press, and the other platen was closed onto the sample at roomtemperature to emboss the sample with the pattern of the expanded metalsheet. Removed from the press, the sample was sprayed with a dilutesolution in trichloroethylene of a polyurethane-based adhesive preparedby capping a polyester macroglycol with a diisocyanate, blocking theisocyanato groups with the oxime of methyl ethyl ketone, and furtherreacting with methylene-bis-orthochloroaniline. The sample was thenplaced in an air-oven at 120 C. for one hour whereupon the diamondscorresponding to the holes of the expanded metal grew thicker fromair-reinflation of the filaments. The embossed outlines did not expand,however, and served to keep the sample consolidated. This heat treatmentalso dried the samples. Although embossed from one side only, there-iniiated samples grew thicker in both directions so as to appear tohave been embossed from both faces.

Sample A employed four superimposed layers of the expanded-metal sheetand was pressed at 500 p.s.i. (35.2 kg./cm.2) for minutes. Thicknesswithin embossed outlines was 0.265 inch (0.67 cm.) for the finalproduct. Assuming this thickness constant over the whole area, densitywas 2.5 lb./ft.3 (0.020 gm./cc.).

Sample B employed iive superimposed layers of the expanded-metal sheetto make a still more flexible product. Applied pressure was 500 p.s.i.(35.2 kg./cm.2) for 5 minutes. Final thickness within the embossedoutlines was about 0.25 inch (0.635 cm.), corresponding to a density ofabout 1.8 1b./ft.3 (0.029 gm./cc.).

Both A and B possessed the thickness, firmness, and resiliencecharacteristic of desirable carpet underlay.

EXAMPLE II A deeply embossed and thermally bonded carpet underlay isdescribed.

Ultramicrocellular polyethylene terephthalate filaments were prepared byextrusion of a uniform foamable solution from a 3-liter cylindricalpressure vessel, through an orifice 0.012 in. (0.305 mm.) in diameterand 0.006 in.

(0.152 mm.) long, and into the ambient atmosphere. Charged to thepressure vessel were:

Dried polyethylene terephthalate (RV=50) gm 1485 With the closedpressure vessel mounted in a box and exposed to hot circulating air,temperature of the contents was raised to 200 C. in 160 min. Thepressure vessel was rotated end-over-end for 400 more minutes untiltemperature reached 220 C. During the next 135 min.. temperature wasreduced to 190 C., after which the contents were allowed to extrudethrough the orifice. Prior to extrusion, a nitrogen ballast pressure of1100 p.s.i.g. (77.4 kg./cm.2 gage) was applied, but this was reduced to525 p.s.i.g. (36.9 kg./cm.2 gage) just before extrusion commenced. Afterbeing heated, the extruded filament had a smooth surface, a roundcross-section, and no skin of dense polymer other than that in exposedcell walls. Apparent density was about 0.020 gm./ cc., diameter about0.070 inch (1.78 mm.), and average cell transverse dimension about 22microns. About 8 to 9 grams of 1,1.2- trichloro-1,2,2-triuoroethane wereretained in the closed cells per 100 gm. of polymer.

The extruded iilaments were laid down randomly but uniformly on a movingscreen belt in such 'a fashion that lengths of dierent area-weights Wereobtained. From the belt, the Iilament batt passed immediately throughthe nip of a roll exerting about 2.0 lbs/in. (0.36 kg./cm.) or' width.This initial consolidation rendered the batt more coherent and easilyhandled without disintegration. The batt was rolled up between layers ofkraft paper, held about 25 minutes, and then embossed. Embossing wasbetween the plates of a flat-bed press. To one of the plates wasfastened a deeply engraved embossing plate with a repetitive, nested,diamond design with 2 inch X 1 inch (5.08 X 2.54 cm.) diagonals andextending to 0.5 inch (1.27 cm.) deep into the plate. Separating eachpattern was an embossing line nominally 0.0625 inch (0.159 cm.1 wide.The other plate of the flat bed press was not modified. Both were heatedto about 250 C. The plates were closed on the batt to an averagedpressure of 45 p.s.i. (3.2 kg./cm.2) and held closed for a time perioddepending on area-weight of the batt being embossed. For 2.5-3.0 02./yd" (S5-102 gm./m.2) batts, about 15 sec. was optimum, increasing to 30sec. for 5.0 oz./yd.2 (170 gm./rn.2) batts. Successful deep embossingand permanent consolidation were obtained over a press plate temperaturerange ot` 250i20 C. Higher temperatures were found to cut through thebatt along embossing lines and/or to melt other parts of the pattern toa solid iilm. Lower temperatures, even at higher pressures and residencetimes, failed to provide permanent consolidation so that delaminationoccurred upon subsequent iilament inflation.

Samples of a range of area-weights were cut from the above product, each11 x 16 inches (27.9 X 40.6 cm.). These samples were placed in a largeautoclave containing 2 ,liters of methylene chloride. Eight pounds (3.63kg.) of peruorocyclobutane were then transferred to the closedautoclave. Heated to 55 |-2 C., autoclave pressures rose to i5 p.s.i.g.(6.3 to 7.0 kg./cm.2 gage). Liquid level was below the samples, but acirculating pump showered the mixed liquid over the samples for 5 min.The liquids were then blown from the autoclave, and the samples wereremoved and dried for 15 min. in an aircirculating oven at 125 C.Filaments cut from the centers of the embossed patterns were found tocontain 15i2 grams of peruorocyclobutane impermeant inflatant per gms.of polymer. None of the 1,1,2-trichloro-1,2,2-trifluoroethane remained.

To silence the noise (scroopiness) of these underlay samples, they weredipped in a silencer solution, drained. and dried for 30 min. in anair-circulating oven at 125 C. Such samples are labeled 11 and 11a inTable Il, and

13 denoted by filled circles in FIGURE 6. Curve d of FIG- UREcorresponds to sample No. 11.

The silencer solution contained: (1) 9 parts of a 40% aqueous emulsionof approximately equal parts of poly- (dimethylsiloxane) andpoly-(methylsiloxane), (2) l part of Dow-Corning Catalyst 21 (a mixtureof dibutyltindilaureate and the zinc salt of Z-ethyl hexoate), and (3)90 parts of distilled water.

Alternatively, the thermally embossed structures were immersed in alatex solution, dried minutes at 125 C. and then given the abovesilencing treatment. I ess silencer was picked up this way, and pigmentdispersed in the latex solutions imparted color to the otherwise Whiteunderlay samples. Samples l0, 10a-f, 12, 12a, and 12b of Table II wereso prepared. Curve c of FIGURE 5 corresponds to sample 10. Open circlesin FIGURE 6 denotes these samples. In no case was latex pick-up sufcientto significantly decrease the amount of open space in the samples. Thelatex solution Was a preparation containing 3 components provided byAlco Chemical Co.

Parts Foamtol BGL-9002 latex (a 58% dispersion in water of a mixture of70 parts of natural rubber and 30 parts of butadiene/styrene (7S/25) co-These three components were dispersed in 900 parts of a surfactantsolution prepared from 100 parts of Aquarex@ ME surfactant, 10 parts ofDaxad 11 dispersing agent, and 890 parts of distilled water. (Aquarex isa registered trademark of E. I. du Pont de Nemours and Co., Inc., fortheir sodium salts of sulfate monoesters of certain mixed higher fattyacids. Daxax is a trademark of Dewey & Almy Chemical Co. for theirpolymerized sodium salts of alkyl aryl and aryl alkyl sulfonic acids.)

A particularly effective silencing of these structures results if theyare sprayed with or dipped in water dispersions of Elvax ethylene/vinylacetate resins and talc, such as those described in Examples III and IV(Elvax is a registered trademark of E. I. du Pont de Nemours and Co.,Inc.). Not only do these dispersions effect silencing, but they are alsoeffective primary binders; and they are relatively inexpensive. Thus,they can constitute the sole binder employed, or they can alternativelybe applied to previously bonded batts.

(0.011 to 0.018 gm./cc.). In general, thicknesses of samples in Table 1Iare equal to or slightly greater than those preferred forcarpet-underlay. Volume fractions of foam in the samples varied fromabout 0.55 to about 0.70. FIG- URES 5 and 6 show that these samplesperform as underlay almost equivalently to the flat sponge-rubberunderlays, which are the best and most expensive of previously availableproducts. Area-weights for sponge-rubber underlays range from about 40to about 80 oZ./yd.2 (about 1360 to 2700 gm./m.2) as compared to the 3.7to 7.1 oz./yd.2 (126 to 241 gm./m.2) range of these samples.

To test recovery and durability under load, these sarnples were indentedover a 1.0 in.2 (6.45 cm?) area with a 200 lb. (90.7 kg.) load for 4.0days. On the average after removal of the load, 46% of the originalthickness was recovered immediately, in 1 day, 76% in 2 days, 88% in 4days, and substantially 100% in the limit.

EXAMPLE III This example is of an embossed carpet underlay prepared witha thermoplastic binder. Because the baths used for introducingimpermeant iniiatant to the foamcells either dissolve or seriouslyweaken such a binder, it was necessary to introduce inflatant gas beforeconsolidation of the laments to a carpet underlay.

The ultramicrocellular filaments used were prepared as described inExample II. A rotating blade mounted below the extrusion die cut thelaments into staple with lengths of 5 il inches (l2.7i2.5 cm.).Peruorocyclobutane impermeant inatant was introduced into the foamcellsby immersing the staple in a bath composed of methylenechloride/perlluorocyclobutane lboiling at 6 C. under atmosphericpressure and containing at least 9% of peruorocyclobutane. After 15minutes in an air-oven at 125 C., the staple was fully inilated with adiameter of about 0.075 inch (1.90 mm.), a density of about 0.015gm./cc., and a peruorocyclobutane level of 14 grams per grams ofpolymer.

A thermoplastic binder dispersion was prepared by mixing together Thisbinder dispersion was sprayed onto the staple, the staple was placed ina box with a 15 X 25 inch t(38.1 x 63.5 cm.) open top, `and the box wasplaced in an oven `at C. until the water in the binder composition hadTABLE )L- PROPERTIES OF THERMALLY CONSOLIDATED AND EMBOSSED UNDERLAYArea Weight (oz./yd.2)(gm.2) Percent Com- (1) pression at Dynamic SampleSilencer Thickness 25 p.s.i. or at; Modulus (p.s.i.) (2) No. Color TotalFilament and Latex (inem-(cm.) 1.76 lig/cm!) (kg/cm?) R.M.A.

10 Goldeuyellow 6.7 (227) 4.2 (142) 2.5 (85) .510 (1. 29) 62.7 392(27.6) 160.5 r 6.2 (210) 4.0 (136) 2.2 (75) .460 (1.17) 65.0 861 (25.4)167.0 5.5 (187) 3.5 (119) 2.0 (68) .490 (1.24) 69.7 438 (30.8) 78.9 7.1(241) 4.6 (156) 2.5 (85) .570 (1. 45) 55.5 425 (29. 9) 225.2 5.9 (200)4.0 (136) 1.9 (64) .430 (1.09) 60.9 538 (37.8) 152.1 5.8 (197) 3.8 (129)2.0 (68) 480 (1.22) 66.8 420 (29.6) 121.1 5.3 3.5 (119) 1.8 (61) 460(1.17) 68.3 390 (27.4) 143.6 3.7 (126) 3.0 (102) 0.7 (24) 430 (1.09)78.7 446 (31.4) 70.7 4.4 (149) 3.5 (119) 0.9 (31) 530 (1. 35) 72.1 456(32.1) 73.2 5.6 3.1 (105) 2.5 (85) .550 (1.40) 68.0 364 (25.6) 140.8 4.0(136) 2.2 (75) 1.8 (61) .470 (1.19) 75.8 391 (27.5) 70.4 4.5 (153) 2.4(81) 2.1 (71) .470 (1.19) 59.6 419 (29.5) 163.3

(1) Obtained using a 4 in.' (25.8 cm) round indentor.

(2) RMA. is a trade-recognized abbreviation for the load in pounds on a50 in.2 (332.6 0111.2) indentor to produce a 25% decrease in thickness.These values were computed by multiplying the 4 in.e load by (5D/4) Themaximum-to-minimum thickness ratios for all of these samples weregreater than 5. Minimum densities computed from area-weight of lamentsand effective (maximum) thickness, Were 0.60 to 0.77 lb./ft.3 (0.0096 to0.0123 gm./ cc.) for the seven 10-coded samples, about 0.56 lb./ft.3(0.0090 gm./cc.) for the ll-coded samples, and 0.39 to 0.47 lb./ft.3(0.0062 to 0.0075 gm./cc.) for the 12-coded samples. Correspondingdensities computed from total area-weight range from .71 to 1.141b./ft.3 75 embossing plate was composed of nested diamond-shapedpatterns, with approximately 1 x 2 inch (2.5 x 5.0 cm.) diagonals whichwere recessed about 0.5 inch (1.27 cm.) into the plate. The raisedembossing lines defining the patterns were about 0.0625 inch (1.50 mrn.)wide. The plates of the press were internally steam-heated to atemperature of about 125 C. Holding the uncompressed batt between theplates reactivated the adhesive, whereupon the plates were closed on thebatt to a pressure of 40 p.s.i. (2.8 kg./cm.2), the steam was turnedoff, and cold water was circulated within the plates until their surfacetemperature reached about 50 C. On removing the sandwich, it was foundto be stably consolidated and to retain the embossed pattern. Thefoam-foils were securely bonded to both surfaces, the one on theembossed face conforming precisely to the embossed pattern.

Area-weight of the embossed, carpet-'underlay specimen was about 6oz./yd.2 (204 gm./m.2) of which both the ultramicrocellular staple andthe binder contributed about 2.5 oz./yd.2 (85 gm./m.2) each. Maximumthickness at the rounded humps of the diamond-shaped patterns was about0.36 inch (0.91 cm.), and minimum thickness along the embossed lines wasabout 0.07 inch (0.18 cm.). These thicknesses corresponded to densitiesof labout 1.4 1b./ft.3 (0.022 grrr/cc.) yand 7.2 lb./ft.3 i(0.115gm./cc.) respectively.

A portion of the carpet-underlay was tested for durability byrepetitively stomping it with `an indentor applying from to 15 p.s.i.(1.05 kg./cm.2) load in cycles of 5 seconds each. An average life-timefor carpet-underlay so treated was estimated to be about 25,000 cycles.At the end of 25,000 cycles of stomping, and after allowing two days forrecovery, 85% of the original thickness was regained in the area oftest. Similarly measured at the end of 200,000 cycles of stomping 74% ofthe original thickness was regained. On another square-inch of thecarpet-underlay, 111 pounds (50.3 kg.) were statically maintained fortwo weeks. During the week following removal of the load, 82% of theoriginal thickness was regained. Excellent cushioning for this underlayis indicated by its immediate compression to only 27.5% of its originalthickness under a load of 200 lb. (90.7 kg.) uniformly distributed overa 10 in.2 (64.5 om?) area. Average tensile strength at failure in thetwo principal directions was about 8 lb./in. (1.43 kg./cm.). Thisstructure is seen to possess excellent durability, resilience, andstrength properties for carpet underlay use.

EXAMPLE IV Wet parts Ethylene/vinyl acetate (67/33) copolymer (50%solids in water) 390 Talc (60% solids in water) 332 Extra Water 1300 Theloosely bonded batt was placed between the fiat plates of 4a hydraulicpress, steam-heated and watercooled as before. The stably consolidatedfiat product was about 0.3 63 in. (0.922 cm.) thick with a density ofabout 0.84 lb./ft.3 l(0.0135 gm./cc.) of which -about 57% wascontributed by foam-filaments and 43% by the binder. The product wasabout 13.5 inches (34.3 cm.) wide yand 22 inches (55.9 cm.) long. Anumber of flat carpet underlay specimens were similarly constructed tohave either or both faces covered with surfacing materials includingkraft paper, polymeric films, foam-foils, net-like fabrics, nonwoventabriCS, and Carpeting- 1 5 EXAMPLE v This example illustrates thatcarpet underlay according to this invention, when maintained stablyconsolidated with a thermoplastic binder, can later be re-expanded to agreater thickness by a simple heat treatment. By overconsolidation, suchproducts yare more easily and inexpensively shipped, to be re-expandedat the point of use.

The same materials and procedures described in Example IV were used toprepare ya flat carpet-underlay specimen about 13.25 inches (33.6 cm.)wide and 21.5 inches (54.6 cm.) long. Its over-consolidated thicknesswas 0.237 inch (0.602 cm.) at a density of about 1.88 lb./ft.3 (0.030gm./Cc.), of which -about 55.6% was contributed by foam-filaments and44.4% by binder. Two rigid expanded-metal plates were clamped overspacers to provide an opening of about 0.75 inch (1.90 cm.), `and thespecimen was slipped into the space between the plates. With theassembly in an air-oven at C., the thermoplastic binder softened toallow the specimen to ll the space. Rebonding occurred on cooling toroom temperature, `and the specimen finally obtained was stablyconsolidated at a thickness of about 0.75 inch (1.90 cm.) and at adensity of about 0.595 -lb./ft.3 (0.0096 grd/cc).

EXAMPLE VI This example illustrates still another method for forming thecushioning products of this invention. A heated blade (or alternativelya spaced assembly of them) is drawn across the surface of the batt tomelt some of the polymer, to smear molten polymer along the line ofpassage, land thereby to create an embossed line which provides thenecessary constraint for stable consolidation. In order that sufficientconstraint be provided by the tiny quantities of polymer which can bemelted, it is necessary that the filaments be fully collapsed, i.e.,have little or no gases within their closed cells. If they are fullyinflated, the gaps between adjacent filament portions are so large thatthe available molten polymer cannot bridge the gaps to provide a stable,coherent, ernbossed line.

Substantially completely collapsed, continuous, ultramicrocellularfilaments were prepared by extruding a 60% solution of polyethyleneterephthalate in methylene chloride through a single orifice 0.015 inch(0.381 mm.) in both diameter and length. Relative viscosity of thepolymer was about 56.5 and it contained only about 58 p.p.m. of water.Extrusion pressure was 800 p.s.i.g. (56.3 kg./" cm.2 gage) at atemperature of about 206-208 C. A sixlayer screen-pack upstream of theorifice contained 20. 100, 20, 200, 20 and 20-mesh screens respectively(U.S. Sieve Series).

A 10 foot (3.05 meter) long, 8 inch (20.3 cm.) diameter metal duct wasswiveled near the extrusion die, its other downward end beingautomatically programmed to traverse the width of a conveyor belt whilesimultaneously moving in a complicated, perpendicular, zig-zag pattern.A downwardly directed jet of air from a 60-90 p.s.i.g. (4.2-6.3 lig/cm.2gage) supply entering the duct about 3 feet (0.91 m.) below the orifice,carried the filament through the duct to randomly deposit it onto themoving conveyor belt. Area-weight of the collected batt was determinedby the speed of the conveyor belt. Downstream from the collection area,the conveyor belt passed beneath a compaction roll exerting about 2pounds/inch (358 gm./cm.) by `which the loose batt was converted into aweakly coherent sheet capable of being wound into a roll.

A portion of the above sheet was selected for conversion to acarpet-underlay specimen. It weighed about 4.9 oZ./yd.2 (166 gm./m.2)and was about 0.13 inch (0.33 cm.) thick. A 2 x 1 x 0.125 inch (5.08 x2.54 x 0.318 cm.) metal blade, coated with polytetrafiuoroethylene resinwas attached to an electrically heated soldering gun so that the firstand last of its above dimensions described the lower surface. Heated bythe soldering gun to about 300 C., the blade was moved in a straightline across the batt at about 8 ft./min. (2.44 JIL/min.) while exertinga force on the batt surface `of about p.s.i. (0.7 kg./cm.2). The heatedblade melted part of the foam along its path, and smeared it along the0.125 inch (0.318 cm.) wide path. Subsequent cooling and solidication ofthe melted polymer securely bound adjacent foam-filaments. In identicalfashion, such lines were formed over the lwhole surface of the battspaced about 2 inches (5.08 cm.) apart. Then the batt was turned over,and parallel lines spaced between those of the other face were formed.Each melted line penetrated about 0.07 inch (0.18 cm.) into the batt,corresponding to about 4 filament layers. Tensile strength at failurefor this collapsed batt Vwas about 10 lb./in. (1.79 kg./cm.). A sectionof this embossed specimen was immersed in a bath containing methylenechloride and peruorocyclobutane for 40 minutes. This bath was aconstant-boiling solution with a boiling point of -6 C. at atmosphericpressure. Removed from the bath, the portion was quickly placed betweentwo metal screens spaced 0.5 inch (1.27 cm.) apart, the assembly beingplaced in a hot-air oven at 125 C. for 15 minutes. Removed from the ovenand the screens, and equilibrated in air, the batt stabilized inthickness at about 0.7 in. (1.8 cm.) and contained in excess of 8 gm. ofperliuorocyclobutane per 100 gm. of polymer. Thickness along the meltedlines was about 0.21 inch (0.533 cm.) indicating that approximately 40%of the polymer along the lines remained cellular.

Another portion of the collapsed batt was similarly embossed andreinfiated, but the two sets of melted lines were formed on the samesurface to intersect diagonally and to produce a repeateddiamond-pattern with diagonals of about 2 x 4 inches (5 x 10.2 cm.). Asindicated by the square point of FIGURE 6, percent compression at 25p.s.i. (1.76 kg./cm.2) for this product was about 72.7% and dynamicmodulus was about 696 p.s.i. (49.0 kg./ cm.2). While both thickness anddynamic modulus for this specimen were higher than preferred, they couldboth be altered in obvious fashion. The broad range of propertiesobtainable in the products of this invention is clearly shown.

EXAMPLE VII This example illustrates the use of cushioning structuresaccording to this invention as the major element in a compositecarpet-underlay. The ultramicrocellular filaments employed were preparedas described in Example II. Unlike Example II, however, the filamentswere postinflated with peruorocyclobutane impermeant inflatant beforeformation of the batts, but the same post-inflation bath, at the sameconditions, was used, followed by airreinflation for 10 minutes at 120C. Following this treatment, the filaments contained about 22 grams ofperfluorocyclobutane per 100 grams of polymer, corresponding to apartial pressure of 320 mm. of mercury and a total gas pressure withinthe cells of about 1.42 atmospheres.

An adhesive formulation and a surfactant formulation were separatelyprovided. The adhesive formulation was 3005 antioxidant dispersion (asused in Example II). The surfactant formulation contained parts of theAquarex@ ME surfactant of Example II, 10 parts of the Daxad IIdispersing agent of Example II, parts of #Z2-4 Heliozone Emulsion assupplied by Lukon, Inc. (Heliozone is a registered trademark `of E. I.du Pont de Nemours and Co., Inc., for emulsions of blended petroleumwaxes melting between 163 and 170 C. as determined by the drop pointmethod), and 890 parts of distilled water. A single binder compositionwas prepared by mixing 272 parts of adhesive formulation, 28.2 parts ofsurfactant formulation, and 625.5 parts of distilled water.

The mold used for consolidating portions of the above filaments `wasentirely of metal coated with polytetrafluoroethylene resin. Onto arigid, expanded metal sheet was placed a 54-mesh screen. Around themargin were placed spacer bars. The portion of filaments was randomlyarranged within the box so formed, and then squeezed into the space byanother screen and expanded metal sheet combination. Although thefilaments were forced to bend around one another to fit the availablespace, they did not lose their filament identity; and the batt so formedhad numerous intercommunicating open channels between filament portions.The above binder composition was air-frothed beneath the mold until itsfroth had risen up through the batt, where the froth collapsed andtended to collect at the crossings of filament portions. The bindercomposition was gelled by passing carbon dioxide gas through the batt,and then cured by heating in air at 125 C. for one hour. Removed fromthe mold, the consolidated batt was 0.33 inch (0.84 cm.) thick, i15%. Itwas cut to a finished size of 11.25 x 16 inches 1.28.6 x 40.6 cm.).

The consoliated batt was placed in another releaseagent-coated frame,and a 20 to mil (0.5 to 1.5 mm.) layer of wet, open-celled, neoprenefroth was doctored on. After l to 2 minutes of gelling time, a thinexpandedmetal sheet was placed onto the foam-layer in order to provide ashallow molded pattern. Covered with a flat steel plate, the frame wasover, and a neoprene-foam coating was similarly doctored onto the otherface of the batt. Drying of the neoprene foam was at 162 C. for 15mintues. The function of the neoprene-foam surfaces was simply toprovide a visually attractive surface. The neoprene foam was producedsubstantially as described in Neoprene Latex, I. C. Carl, E. I. du Pontde Nemours and Co., Inc., 1962, p. 91. It was based on neoprene T-60latex (Du Pont), and incorporated various dyes for attractivecoloration. The formulation shown was modified by the addition, in theamount of 20 parts per 100 of T-60 latex solids, of PAPI@ polymethylenepolyphenylisocyanate as produced by the Carwin Div. of The Upjohn Co.This additive has about 2.7 to 2.8 isocyanato groups per molecule. Amongother advantages, this addition imparts very short gel times to thefrothed foam and permits of room-temperature curing.

Six carpet-underlay specimens were prepared as described, and theirproperties are shown in Table III. Specimen code 7 denotes golden-yellowneoprene foam, code 8 denotes white, and code 9 denotes green.

TABLE IIL-ADHESIVELY BONDED UNDERLAY SURFACED WITH NEOPRENE FOAM (l)Percent Compression at Dynamic Sample Latex Neoperene Thickness 25p.s.i. or at Modulus [p.s.i. (2) No. Total Filament Binder FoamIinch-(cm.)l 1.76 Lrg/cm.2 (kg./crn.2)] R.M.A.

(l) Obtained using a 4 111.2 (25.8 cm?) round indentor. l (2) R.M.A. isa trade-recognized abbreviation-for the load in pounds on a 50 in.2(322.6 cm.2) iudentor to produce a 25% decrease 1n thickness. Thesevalues were obtained by multiplying the 4 in.2 load by (50/4).

composed of 182.5 parts of Foamtol BGL-9002 latex,

Dynamic modulus versus percent compression for these 10 parts ofITV-2003 curing agent, and 12 parts of FZ- 75 six carpet-underlyspecimes is indicated by small xs in FIGURE 6. Load-compression behaviorfor sample No. 7 is shown by curve b of FIGURE 5, and curve acorresponds to sample No. 9. Although not shown, load-compression forsample No. 8 closely approximates curve c. Except for slightlyincreasing the extent of compression at a given load, the neoprene foamhad substantially no effect on the carpet-underlay performanceproperties. Also suitable for surfacing these carpet underlays arevarious flexible polyurethane foams. They can either be foamed in placeor be adhesively bonded to the surface as foils of previously foamedmaterial.

What is claimed is:

1. A resilient, low-density, web-like cushioning structure, suitable ascarpet-underlay, comprised of closedcell, pneumatic, polymeric, cellularmaterial in filamentary form, saidlamentary material being randomlydisposed within said structure to provide numerous crossings of lamentportions, being consolidated so as to distort lament portions around oneanother and provide substantial areas of lament-to-lament engagementsuch that the average ratio of Volume of said lamentary material tototal volume of said structure is at least 0.4, and being bonded atleast within portions of said structure to permanently retain saidconsolidated volume, major portions of said tilamentary material havinga density of from about 0.008 to 0.06 gm./cc. and containing within thecells thereof about 6 to 40 gm. of an impermeant inflatant per 100 gm.of polymer.

2. Structure according to claim 1 having a thickness of about 0.1 to 1.0inch and a weight, of lilamentary material only, of about 1.0 to 10oz./yd.2

3. Structure according to claim 1 in which the cellular material isultramicrocellular exhibiting uniform texture and uniplanar orientation.

4. Structure according to claim 3 in which the said polymer ispolyethylene terephthalate.

5. Structure according to claim 1 in which said impermeant inflatant isselected from the group consisting or' sulfur hexauoride and saturatedaliphatic and cycloaliphatic compounds having at least onefluorine-to-carbon covalent bond.

6. Structure according to claim 5 in which said impermeant inatant isperfluorocyclobutane.

7. Structure according to claim 1 wherein said filament portions have amajor cross-sectional dimension of about 0.025 to 0.25 inch.

8. Structure according to claim 1 wherein the filamentary material isfusion bonded and densied in a pattern of line elements across and alongthe structure.

9. Structure according to claim 1 wherein the lamentary material isbonded by an adhesive.

References Cited UNITED STATES PATENTS 3,227,664 l/l966 Blades et al.

2,464,301 3/1949 Francis 161-159 X 3,080,580 3/1963 Tobari 51-3613,106,507 1'0/1963 Richmond l6l-l78 X 3,179,551 4/1965 Dudas 156-209 X3,278,954 10/1966 Barhite 161-170 X 3,344,221 9/1967 Moody etal ll-159 XROBERT F. BURNETT, Primary Examiner L. M. CARLIN, Assistant ExaminerU.S. Cl. X.R.

